Crown reinforcement for a radial tire

Abstract

The invention relates to a tire in which at least one first profiled element P of rubber mix separates the axially widest ply of reinforcement elements from at least one end of a second ply, axially narrower than the axially widest ply, the axially outer end of said first profiled element P being located at a distance from the equatorial plane of the tire which is less than the distance between said plane and the end of the axially widest ply of reinforcement elements, said profiled element P being radially separated at least in part from the liner C of said axially narrower ply of reinforcement elements by a second profiled element of rubber mix G, and said first and second profiled elements of rubber mix P and G and said liner C having secant modules of elasticity under tension at 10% elongation MP, MG, MC respectively such that MC≧MG>MP.

Description

[0001]This application is a U.S. Continuation Application under 35 USC 371 of International Application PCT / EP2004 / 001362 filed Feb. 13, 2004.BACKGROUND OF THE INVENTION[0002]The present invention relates to a tire having a radial carcass reinforcement, and more particularly to a tire intended to be fitted on vehicles bearing heavy loads and traveling at sustained speed, such as, for example, lorries, tractors, trailers or highway buses.[0003]Generally, the carcass reinforcement is anchored on either side in the zone of the bead and is radially surmounted by a crown reinforcement formed of at least two plies, which are superposed and formed of cords or cables which are parallel within each ply. It also generally comprises a ply of metal wires or cables of low extensibility which form an angle of between 45° and 90° with the circumferential direction, this ply, referred to as a triangulation ply, being radially located between the carcass reinforcement and the first, so-called workin...

AI Technical Summary

Benefits of technology

"The invention is a tire with a radial carcass reinforcement and a crown reinforcement that includes at least two plies of reinforcement elements. The tire has a radially outer element that is axially narrower than the axially widest ply. The tire also has two layers of rubber mixes that are designed to improve resistance to separation between the ends of the plies. The rubber mixes have different elasticity modules to create a decoupling effect that protects the end of the narrowest ply and delays the appearance of delamination. The total thickness of the profiled elements of the rubber mixes is between 10% and 80% of the overall thickness of the rubber mixes. The distance between the two plies is between 3.5 and 5. The axial width of the profiled elements of the rubber mixes is between the diameter of the reinforcement elements of the axially narrowest ply and the axially widest ply. The engagement between the profiled elements of the rubber mix and the axially narrowest ply is between 10 and 20. The invention provides a tire with improved resistance to separation between the plies and reduced delamination at the ends of the plies."

Problems solved by technology

All the conditions under which such a tire is required to travel without doubt make it possible to increase the number of kilometers traveled, the wear of the tire being less; on the other hand, the endurance of the latter, and in particular of the crown reinforcement, is greatly impaired.

The stresses existing at the level of the crown reinforcement, and more particularly the shearing stresses between the crown plies, combined with a non-negligible increase in the operating temperature at the ends of the axially shortest working ply, result in the appearance and propagation of cracks in the rubber at said ends, despite the presence of a thickened layer of rubber at the junction of the edges of the working crown plies.

The same problem exists in the case of edges of two plies having reinforcement elements, said other ply not necessarily being radially adjacent to the first.

It was noted that the various structures listed above did not provide a completely satisfactory solution under conditions of travel which are highly disadvantageous to the tire.

Images